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24 | // ******************************************************************** |
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25 | // |
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26 | // $Id: G4PolarizedPairProductionCrossSection.cc,v 1.5 2007/11/01 17:32:34 schaelic Exp $ |
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27 | // GEANT4 tag $Name: geant4-09-02-ref-02 $ |
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28 | // |
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29 | // ------------------------------------------------------------------- |
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30 | // |
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31 | // GEANT4 Class file |
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32 | // |
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33 | // |
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34 | // File name: G4PolarizedPairProductionCrossSection |
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35 | // |
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36 | // Author: Andreas Schaelicke on the base of Karim Laihems code |
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37 | // |
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38 | // Creation date: 16.08.2006 |
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39 | // |
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40 | |
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41 | #include "G4PolarizedPairProductionCrossSection.hh" |
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42 | // #include "G4PolarizedGammaConversionModel.hh" |
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43 | // #include "G4Element.hh" |
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44 | |
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45 | G4bool G4PolarizedPairProductionCrossSection::scrnInitialized=false; |
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46 | G4double G4PolarizedPairProductionCrossSection::SCRN [3][20]; |
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47 | // screening function lookup table; |
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48 | |
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49 | void G4PolarizedPairProductionCrossSection::InitializeMe() |
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50 | { |
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51 | if (!scrnInitialized) { |
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52 | SCRN [1][1]= 0.5 ; SCRN [2][1] = 0.0145; |
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53 | SCRN [1][2]= 1.0 ; SCRN [2][2] = 0.0490; |
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54 | SCRN [1][3]= 2.0 ; SCRN [2][3] = 0.1400; |
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55 | SCRN [1][4]= 4.0 ; SCRN [2][4] = 0.3312; |
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56 | SCRN [1][5]= 8.0 ; SCRN [2][5] = 0.6758; |
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57 | SCRN [1][6]= 15.0 ; SCRN [2][6] = 1.126; |
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58 | SCRN [1][7]= 20.0 ; SCRN [2][7] = 1.367; |
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59 | SCRN [1][8]= 25.0 ; SCRN [2][8] = 1.564; |
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60 | SCRN [1][9]= 30.0 ; SCRN [2][9] = 1.731; |
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61 | SCRN [1][10]= 35.0 ; SCRN [2][10]= 1.875; |
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62 | SCRN [1][11]= 40.0 ; SCRN [2][11]= 2.001; |
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63 | SCRN [1][12]= 45.0 ; SCRN [2][12]= 2.114; |
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64 | SCRN [1][13]= 50.0 ; SCRN [2][13]= 2.216; |
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65 | SCRN [1][14]= 60.0 ; SCRN [2][14]= 2.393; |
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66 | SCRN [1][15]= 70.0 ; SCRN [2][15]= 2.545; |
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67 | SCRN [1][16]= 80.0 ; SCRN [2][16]= 2.676; |
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68 | SCRN [1][17]= 90.0 ; SCRN [2][17]= 2.793; |
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69 | SCRN [1][18]= 100.0 ; SCRN [2][18]= 2.897; |
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70 | SCRN [1][19]= 120.0 ; SCRN [2][19]= 3.078; |
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71 | |
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72 | scrnInitialized=true; |
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73 | } |
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74 | } |
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75 | |
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76 | G4PolarizedPairProductionCrossSection::G4PolarizedPairProductionCrossSection() |
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77 | { |
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78 | InitializeMe(); |
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79 | } |
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80 | |
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81 | |
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82 | void G4PolarizedPairProductionCrossSection::Initialize(G4double aGammaE, |
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83 | G4double aLept0E, |
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84 | G4double sintheta, |
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85 | const G4StokesVector & beamPol, |
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86 | const G4StokesVector & /*p1*/, |
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87 | G4int /*flag*/) |
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88 | { |
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89 | G4double aLept1E = aGammaE - aLept0E; |
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90 | |
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91 | G4double Stokes_P3 = beamPol.z() ; |
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92 | // ************************************************************************** |
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93 | |
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94 | G4double m0_c2 = electron_mass_c2; |
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95 | G4double Lept0E = aLept0E/m0_c2+1., Lept0E2 = Lept0E * Lept0E ; |
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96 | G4double GammaE = aGammaE/m0_c2; |
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97 | G4double Lept1E = aLept1E/m0_c2-1., Lept1E2 = Lept1E * Lept1E ; |
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98 | |
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99 | |
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100 | // const G4Element* theSelectedElement = theModel->SelectedAtom(); |
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101 | |
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102 | // ******* Gamma Transvers Momentum |
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103 | |
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104 | G4double TMom = std::sqrt(Lept0E2 -1.)* sintheta, u = TMom , u2 =u * u ; |
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105 | G4double Xsi = 1./(1.+u2) , Xsi2 = Xsi * Xsi ; |
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106 | |
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107 | // G4double theZ = theSelectedElement->GetZ(); |
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108 | |
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109 | // G4double fCoul = theSelectedElement->GetfCoulomb(); |
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110 | G4double delta = 12. * std::pow(theZ, 1./3.) * Lept0E * Lept1E * Xsi / (121. * GammaE); |
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111 | G4double GG=0.; |
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112 | |
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113 | if(delta < 0.5) { |
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114 | GG = std::log(2.* Lept0E * Lept1E / GammaE) - 2. - fCoul; |
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115 | } |
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116 | else if ( delta < 120) { |
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117 | for (G4int j=2; j<=19; j++) { |
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118 | if(SCRN[1][j] >= delta) { |
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119 | GG =std::log(2 * Lept0E * Lept1E / GammaE) - 2 - fCoul |
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120 | -(SCRN[2][j-1]+(delta-SCRN[1][j-1])*(SCRN[2][j]-SCRN[2][j-1])/(SCRN[1][j]-SCRN[1][j-1])); |
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121 | break; |
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122 | } |
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123 | } |
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124 | } |
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125 | else { |
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126 | G4double alpha_sc = (111 * std::pow(theZ, -1./3.)) / Xsi; |
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127 | GG = std::log(alpha_sc)- 2 - fCoul; |
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128 | } |
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129 | |
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130 | if(GG<-1) GG=-1; // *KL* do we need this ?! |
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131 | |
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132 | |
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133 | G4double I_Lepton = (Lept0E2 + Lept1E2)*(3+2*GG) + 2 * Lept0E * Lept1E * (1 + 4 * u2 * Xsi2 * GG); |
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134 | |
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135 | // G4double D_Lepton1 = -8 * Lept0E * Lept1E * u2 * Xsi2 * GG / I_Lepton; |
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136 | |
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137 | G4double L_Lepton1 = GammaE * ((Lept0E - Lept1E) * (3. + 2. * GG)+2 * Lept1E * (1 + 4 * u2 * Xsi2 * GG))/I_Lepton; |
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138 | |
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139 | G4double T_Lepton1 = 4 * GammaE * Lept1E * Xsi * u * (1. - 2. * Xsi) * GG / I_Lepton ; |
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140 | |
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141 | |
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142 | G4double Stokes_S1 = (Stokes_P3 * T_Lepton1) ; |
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143 | G4double Stokes_S2 = 0; |
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144 | G4double Stokes_S3 = (Stokes_P3 * L_Lepton1) ; |
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145 | |
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146 | |
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147 | theFinalElectronPolarization.setX(Stokes_S1); |
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148 | theFinalElectronPolarization.setY(Stokes_S2); |
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149 | theFinalElectronPolarization.setZ(Stokes_S3); |
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150 | |
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151 | if(theFinalElectronPolarization.mag2()>1) { |
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152 | G4cout<<" WARNING in pol-conv theFinalElectronPolarization \n"; |
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153 | G4cout |
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154 | <<"\t"<<theFinalElectronPolarization |
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155 | <<"\t GG\t"<<GG |
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156 | <<"\t delta\t"<<delta |
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157 | <<G4endl; |
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158 | theFinalElectronPolarization.setX(0); |
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159 | theFinalElectronPolarization.setY(0); |
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160 | theFinalElectronPolarization.setZ(Stokes_S3); |
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161 | if(Stokes_S3>1) theFinalElectronPolarization.setZ(1); |
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162 | } |
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163 | |
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164 | |
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165 | G4double L_Lepton2 = GammaE * ((Lept1E - Lept0E) * (3. + 2. * GG)+2 * Lept0E * (1 + 4 * u2 * Xsi2 * GG))/I_Lepton; |
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166 | |
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167 | G4double T_Lepton2 = 4 * GammaE * Lept0E * Xsi * u * (1. - 2. * Xsi) * GG / I_Lepton ; |
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168 | |
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169 | G4double Stokes_SS1 = (Stokes_P3 * T_Lepton2) ; |
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170 | G4double Stokes_SS2 = 0; |
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171 | G4double Stokes_SS3 = (Stokes_P3 * L_Lepton2) ; |
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172 | |
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173 | theFinalPositronPolarization.SetPhoton(); |
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174 | |
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175 | theFinalPositronPolarization.setX(Stokes_SS1); |
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176 | theFinalPositronPolarization.setY(Stokes_SS2); |
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177 | theFinalPositronPolarization.setZ(Stokes_SS3); |
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178 | |
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179 | if(theFinalPositronPolarization.mag2()>1) { |
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180 | G4cout<<" WARNING in pol-conv theFinalPositronPolarization \n"; |
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181 | G4cout |
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182 | <<"\t"<<theFinalPositronPolarization |
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183 | <<"\t GG\t"<<GG |
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184 | <<"\t delta\t"<<delta |
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185 | <<G4endl; |
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186 | } |
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187 | } |
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188 | |
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189 | G4double G4PolarizedPairProductionCrossSection::XSection(const G4StokesVector & /*pol2*/, |
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190 | const G4StokesVector & /*pol3*/) |
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191 | { |
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192 | G4cout<<"ERROR dummy routine G4PolarizedPairProductionCrossSection::XSection called \n"; |
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193 | return 0; |
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194 | } |
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195 | |
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196 | // return expected mean polarisation |
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197 | G4StokesVector G4PolarizedPairProductionCrossSection::GetPol2() |
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198 | { |
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199 | // electron/positron |
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200 | return theFinalElectronPolarization; |
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201 | } |
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202 | G4StokesVector G4PolarizedPairProductionCrossSection::GetPol3() |
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203 | { |
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204 | // photon |
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205 | return theFinalPositronPolarization;; |
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206 | } |
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207 | |
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208 | |
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